1. Field of the Invention
The present disclosure relates to actuators for rotor blades of helicopters. More specifically, the present disclosure relates to a hybrid actuator for main rotor blade control flaps.
2. Description of Related Art
The operation and performance of helicopter rotor blades is significant to the overall performance of a helicopter. The vertical lift and the forward and lateral movement of the helicopter are all made possible by the operation of the rotor blades. A swashplate located around the rotating shaft of a helicopter is conventionally used to mechanically control the movement of blades by producing their pitch for rotor thrust control (tilt of thrust and thrust magnitude). The traditional method for producing the pitch motion is by directly driving at the blade root via the swashplate. But, the swashplate is an extremely complex, very heavy and maintenance intensive mechanical system. The elimination of the swashplate can result in many benefits such as reduced empty weight and drag, and increased maintainability.
Recently, on-blade control flaps have been used on the main rotor blades of helicopters to reduce the required power of actuation by controlling the pitch motion and higher harmonics of the blades during flight. Instead of the swashplate, the control flaps are driven by on-blade actuators, particularly, electromechanical actuators, that produce the pitch motion of the blades by directly driving at the flap. The control flaps deflect to induce a hinge moment on the blade via the aerodynamics of the air stream acting on the flap. This moment then generates the required pitch motion of the blade about the blade pitch axis with an order of magnitude less power than direct pitching of the blade. The control flaps can be used for both primary flight control (PFC) as well as vibration reduction and acoustic noise reduction. The flaps eliminate the need for a swashplate, swashplate linkages, main rotor servo flaps, pitch links, main rotor bifilar, and the associated hydraulic system. Unfortunately, prior art on-blade electromechanical actuators have not proven effective and thermally efficient for high harmonic control (HHC), which involves high frequency and low amplitude flapping of the flaps. Additionally, prior art on-blade actuators have proven to be very maintenance intensive.
Accordingly, there is need for on-blade actuation mechanisms that overcome, mitigate and/or alleviate one or more of the aforementioned and other deleterious effects of the prior art.